Solid fossil fuels such as coal often are ground in order to render the solid fossil fuel suitable for certain applications. Grinding the solid fossil fuel can be accomplished using a device referred to by those skilled in the art as a pulverizer. One type of pulverizer suited for grinding is referred to as a “bowl mill pulverizer”. This type of pulverizer obtains its name by virtue of the fact that the pulverization that takes place therein is effected on a grinding surface that in configuration bears a resemblance to a bowl. In general, a bowl mill pulverizer comprises a body portion on which a grinding table is mounted for rotation. Grinding rollers mounted on suitably supported journals interact with the grinding table to effect the grinding of material interposed therebetween. After being pulverized, the particles of material are thrown outwardly by centrifugal force, whereby the particles are fed into a stream of warm air and blown into other devices for separation by particle size.
Grinding rollers are urged toward the grinding table against the fossil fuel being ground by a spring assembly. The force that this exerts may be manually adjusted. The greater the force, the finer the particle size of the fossil fuels being ground.
Coal pulverizers operating under low load conditions when there isn't enough coal feed to develop a stable coal bed causes rough operation. Rough operation causes high bending stresses to be placed on a main vertical shaft of the pulverizer, which can result in its failure. These stresses are also high enough that many component failures have been attributed to such rough operation. Relief spring assemblies have been used in the past on deep bowl mills to reduce such stresses at times of rough operation. However, such spring, assembly arrangements are not possible on shallow bowl mills due to the very small space available working within existing journal and journal opening cover spaces.
It is important that any solution to this existing rough operation issue is capable of implementation within existing journal and journal opening cover spaces due to the expense of otherwise replacing such equipment. Accordingly, any solution must be able to be used with or “retrofitted” to fit within existing journal space and existing journal opening cover space of a shallow bowl mill.